Washing apparatus and drain pump

ABSTRACT

A pump ( 22 ) includes a pump casing ( 34 ) having a pump chamber ( 40 ), an impeller ( 30 ) received in the pump chamber ( 40 ), an electric motor ( 28 ) for driving the impeller ( 30 ), a detector ( 96 ) being configured for detecting a load on the pump ( 22 ), and a speed regulator ( 98 ) coupled to the detector. The speed regulator ( 98 ) is configured for decreasing the speed of the motor ( 28 ) to a speed greater than zero in response to the detector ( 96 ) detecting an unload condition of the drain pump ( 22 ).

CROSS REFERENCE TO RELATED APPLICATIONS

This non-provisional patent application claims priorities under 35 U.S.C. § 119(a) from Patent Application No. 201210218760.0 filed in The People's Republic of China on 28 Jun., 2012 and Patent Application No. 201320168365.6 filed in The People's Republic of China on 7 Apr., 2013.

FIELD OF THE INVENTION

This invention generally relates to a drain pump which is especially suitable for a washing apparatus such as a dishwasher or a washing machine.

BACKGROUND OF THE INVENTION

Centrifugal pumps are often used as drain pumps in washing machines and dishwashers. In application, the pump is mounted inside the machine and activated automatically by a control circuit of the machine, mainly to pump out water from the machine. The operation can be divided into three stages: the starting stage, the full water stage and the air-water stage, The air-water stage is the last stage during which most of the water has already been pumped out and only residual water mixed with air flows through the pump. In general, the air-water stage is the noisiest phase of operation, with the noise level significantly greater than the noise levels of the starting and full water stages.

Drain pumps are usually driven by single-phase synchronous motors which have a long life and a simple construction. Being a single-phase synchronous motor, the motor can start in either direction and thus, vanes of the impeller of the pump are designed as radially extended straight vanes so that the impeller can operate in both directions. However, the straight vanes cause the hydraulic efficiency of the drain pumps to be low.

Therefore, there is desirable to have a quieter and more efficient drain pump.

SUMMARY OF THE INVENTION

Accordingly, in one aspect thereof, the present invention provides a washing apparatus including a washing chamber, a water supply path for supplying fresh water to the washing chamber, a drain path for discharging waste water in the washing chamber to the outside; and a drain pump for removing the waste water via the drain path. The drain pump includes a pump casing having a pump chamber, an impeller received in the pump chamber; and a brush direct current motor which comprises a rotor and a stator. The rotor comprises a shaft coupled to the impeller, a rotor core fixed on the shaft, a commutator fixed on the shaft adjacent the rotor core, and rotor windings wound on the rotor core and electrically connected to the commutator. The stator comprising a magnetically conductive housing, at least one permanent magnet fixed to the housing, at least one pair of brushes making slide contact with the commutator, and at least two terminals for coupling an external direct current power supply to the brushes.

According to a preferred embodiment, further comprises a detector being configured for detecting a load on the drain pump and a speed regulator coupled to the detector and being configured for decreasing the speed of the motor to a speed greater than zero in response to the detector detecting an unload condition.

Preferably, the impeller comprises a base plate and a plurality of curved vanes disposed on the base plate.

Preferably, the pump casing is in a spiral shape.

Preferably, the drain pump further comprises a macerator disposed in the pump chamber and fixed to the shaft of the motor.

Preferably, the pump casing comprises a side wall and a top wall forming an annular step, the inlet extending outwardly from the top wall and the outlet extending outwardly from the side wall.

Optionally, the brush direct current motor is a high voltage brush direct current motor with a direct current power between 50˜400 volt being supplied.

Optionally, the brush direct current motor is a low voltage brush direct current motor with a direct current power between 4-36 volt being supplied.

Optionally, the flow rate of the drain pump is smaller than 60 litres per minute.

Optionally, an outer diameter of the magnetically conductive housing is between 35 mm-60 mm and an output power of the brush direct current motor is smaller than 60 watts.

In another aspect thereof, the present invention provides a drain pump comprising a spiral volute having a pump chamber, an impeller received in the pump chamber and comprising a base plate and a plurality of curved vanes disposed on the base plate, a macerator disposed in the pump chamber and fixed to the shaft, and a brush direct current motor having a rotor and a stator. The rotor comprises a shaft coupled to the impeller, a rotor core fixed on the shaft, a commutator fixed on the shaft adjacent the rotor core, and rotor windings wound on the rotor core and electrically connected to the commutator. The stator comprises a magnetically conductive housing, at least one permanent magnet fixed to the housing, at least one pair of brushes making slide contact with the commutator, and at least two terminals for coupling an external direct current power supply to the brushes.

In a third aspect thereof, the present invention provides a pump comprising a pump casing having a pump chamber, an impeller received in the pump chamber, an electric motor for driving the impeller, a detector being configured for detecting a load on the pump, and a speed regulator coupled to the detector. The speed regulator is configured for decreasing the speed of the motor to a first speed greater than zero and smaller than a second speed when the detector detects the pump operates in a unload condition, the brush direct current motor operating in the second speed during a full load condition of the pump.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention are described, by way of example only, with reference to the drawings, in which identical or related structures, elements, or parts may be labeled with the same reference numerals throughout the figures. Dimensions of components and features shown in the figures are generally chosen for convenience and clarity of presentation and are not necessarily shown to scale.

FIG. 1 schematically illustrates a washing apparatus incorporating a drain pump in accordance with an embodiment of the present invention;

FIG. 2 illustrates an assembled view of the drain pump shown in FIG. 1;

FIG. 3 illustrates an axially sectional view of the drain pump shown in FIG. 2;

FIG. 4 illustrates an impeller being a part of the drain pump shown in FIG. 2; and

FIG. 5 illustrates a block diagram of a control system for the drain pump shown in FIG. 2.

DETAILED DESCRIPTION OF THE VARIOUS EMBODIMENTS

Referring to FIG. 1, a washing apparatus 10, such as a dishwasher or a washing machine, has a washing chamber 12, a water supply path 14 for supplying fresh water to the washing chamber 12, a drain path 16 for discharging waste water to the outside, a circulating path 18 for re-circulating the water with detergent to the washing chamber 12, and a pump system 20 having a drain pump 22 and a circulating pump 24. The drain pump 22 removes the liquid in the washing chamber 12 via the drain path 16 and the circulating pump 24 circulates the liquid within the washing chamber 12 via the circulating path 18.

Referring to FIGS. 2 and 3, the drain pump 22 includes an electric motor 28 with an output shaft 26, an impeller 30 fixedly mounted to the output shaft 26, a base 32, and a spiral volute 34 with an inlet 36 and an outlet 38. The volute 34 is assembled to the base 32. A sealing ring 33 is arranged between the base 32 and the volute 34. The base 32 and the volute 34 define a pump chamber 40 for receiving the impeller 30. The inlet 36 and the outlet 38 are in fluid communication with the pump chamber 40. The inlet 36 extends outwardly from a top wall 42 of the volute 34 in the axial direction of the shaft 26. The outlet 38 extends outwardly from a sidewall 44 of the volute 34. Liquid in the washing chamber 12 enters into the pump chamber 40 via the inlet 36 and then is pumped out from the drain path 16 via the outlet 38 under the pressure generated by the impeller 30.

Preferably, the top wall 42 forms an annular step 46 in the inner surface thereof. The inlet 36 outwardly extends from the outer surface 47 of the top wall 42. The annular step 46 provides an abrupt change in the inner surface of the top wall 42, causing the fluid to be abruptly deflected to create greater turbulence or mixing of the fluid in the pump chamber 40 to finely disperse the air throughout the water. As such, the finely mixed air and water provide a constant load on the impeller 30, whereby the noise created by the pump sounds continuous or constant rather than intermittent. Compared to the intermittent noise, this constant noise has a relatively consistent frequency or better sound quality and is easier to accept.

Also referring to FIG. 4, the impeller 30 includes a circular base plate 48 and a plurality of vanes 50 uniformly disposed on the base plate 48 in the circumferential direction of the shaft 26. The base plate 48 has a hub which comprises a mounting post 54 with a mounting hole 52 (shown in FIG. 3) and a cone 56 extending radially from the mounting post 54. The shaft 26 of the motor 28 is inserted through the mounting hole 52 and a macerator 51 is optionally fixed on the tip of the shaft 26. The shaft 26 is press-fitted in the mounting hole 52 so that the impeller 30 is fixed on the shaft 26. The macerator 51 rotates with the shaft 26 to break down the food residual in the pump chamber 40. The vanes 50 extend from the cone 56, along a curved path, to the radially outer surface 64 of the base plate 48 and are aligned flush with the radially outer surface 64 in the axial direction. Each vane 50 has a radially inner edge 58, a radially outer edge 60, and a leading edge 62 connecting the radially inner edge 58 and the radially outer edge 60. The radially inner edge 58 is inclined with respect to the axial direction and forms an obtuse corner 66 with the leading edge 62.

Referring to FIG. 3, the motor 28 is preferably a high voltage direct current (HVDC) motor comprising a stator and a rotor. The rotor comprises the shaft 26, a rotor core 68 fixed on the shaft 26, a commutator 70 fixed on the shaft 26 adjacent the rotor core 68, and rotor windings (not shown) wound about poles of the rotor core 68 and electrically connected to the commutator 70. Outer surfaces of the rotor poles form a circle. Slots are formed between adjacent rotor poles for accommodating the rotor windings. A fan 74 is fixed to the rotor core 68 and co-operates with openings 78 in a housing 76 of the motor 28 to create air flow to cool the motor 28 when rotating. Preferably, the rotor core 68 is formed by axially stacking a plurality of rotor laminations and has twelve slots. The commutator 70 has twenty-four commutator segments.

The stator comprises an axially extending round housing 76 having an open end and a closed end 80 opposite to each other, permanent magnets 82 fixed to the inner surface of the housing 76, an end cap 84 closing the open end of the housing 76, and a pair of brush assemblies. The housing 76 is made of magnetically conductive material. The end cap 84 is fixedly mounted to the housing 76. The shaft 26 is supported by two bearings 88 respectively located on the end cap 84 and the closed end 80 of the housing 76 with the rotor core 68 facing the permanent magnets 82. An air gap is formed between the rotor core 68 and the permanent magnets 82. Each brush assembly has a brush cage 90 arranged on the end cap 84. A brush 92 is slidably received in the brush cage 90 and urged by a resilient member or spring (not shown) into sliding contact with the commutator 70. Two electrical terminals 94 for electrically connecting to an external power supply are supported by the end cap 84. Each electrical terminal 94 is electrically connected to a corresponding brush 92 via a conductor (not shown). Thus, a high voltage direct current power preferably between 50˜400 volts can be supplied to the rotor windings via the electrical terminals 94, the brushes 92 and the commutator 70.

The housing 76 of the motor 28 is assembled to the base 32 of the pump 22 via a mounting plate 86. A boss 81 is formed in the center of the mounting plate 86 and receives a bearing holder 83 of the closed end 80 of the motor 28. An annular protrusion 85 axially extends from the bottom surface of the base 32 facing the motor 28. A flange 87 is formed on a periphery of the bottom surface of the annular protrusion 85 and receives the boss 81 of the mounting plate 86. The axial surface of the boss 81 facing the base 32 and the inner surface of the annular protrusion 85 define a seat 89. A seal 91 tightly sleeved on the shaft 26 is disposed in the seat 89. Preferably, the seal 91 is made of ceramics or rubber.

FIG. 5 illustrates a block diagram of a control system for the drain pump 22. The control system comprises a detector 96, a speed regulator 98, and an on-off control means (not shown). The on-off control means is preferably incorporated into a central controller (not shown) of the washing apparatus 10 and configured to start or stop the drain pump 22 according to the predetermined processes of the washing apparatus 10. The on-off control means can be realized in known technology and will not be described in detail herein. The detector 96 and the speed regulator 98 are preferably arranged on a circuit board mounted to the motor 28. The detector 96 is configured to detect the load on the drain pump 22. The speed regulator 98 is configured to decrease the speed of the motor 28 to a first speed greater than zero and smaller than a second speed when the detector 96 detects the drain pump 22 to operate in an unload state. The motor 28 operates in the second speed during the full load state of the drain pump 22. By this configuration, when the situation that the waste water in the washing chamber 12 is drained (namely the drain pump 28 operates in the unload state) before the central controller of the washing apparatus 10 stops the drain pump 22, the speed regulator 96 can decrease the speed of the motor 28 to be smaller than the speed of the motor 28 during the full load state of the drain pump 22, which is able to reduce the noise of the drain pump 22. On the other hand, configuring the speed of the motor 28 to be greater than zero makes the on-off control for the drain pump 28 is only executed by the central controller of the washing machine 10 without interference, which ensures the washing machine 10 to correctly operate according to the predetermined processes. Preferably, the detector 96 detects the load of the drain pump 22 by detecting the current flowing through the motor 28. The speed regulator 98 decreases the speed of the motor 28 by reducing the direct current power supplied to the motor 28.

In another embodiment, the motor 28 of the drain pump 22 may be a low voltage direct current (LVDC) motor with a low voltage direct current power between 4-36 volts being supplied. The LVDC motor may have a similar structure as the HVDC motor. The drain pump 22 with the LVDC motor 28 is especially suitable for a small and/or low cost washing apparatus 10 where the drain pump 22 has a low flow rate. Preferably, the output power of the LVDC motor 28 is smaller than 60 watts. The outer diameter of the stator housing 76 of the LVDC motor 28 is between 35 mm-60 mm. The water flow rate of the drain pump 22 is smaller than 60 litres per minute (LPM). In an example of a table top dishwasher, the output power of the LVDC motor 28 is smaller than 20 watts, the outer diameter of the stator housing 76 is between 35 mm-50 mm and the water flow rate of the drain pump 22 is smaller than 30 LPM. Preferably, the LVDC motor 28 is a 2 poles 3 slots motor. Optionally, the LVDC motor 28 may be a 2 poles 5 slots or 2 poles 7 slots motor.

Unlike in a conventional drain pump driven by a single-phase synchronous motor, in a drain pump in accordance with the embodiments of the present invention, the rotating direction of the HVDC motor or LVDC motor 28 is controllable, so the vanes 50 of the impeller 30 is allowed to be curved and the volute 34 may be accordingly in a spiral shape. Therefore the hydraulic efficiency of the pump 22 can be improved. Secondly, as the speed of the synchronous motor is fixedly proportional to the frequency of its power supply, the speed of the synchronous motor can not adjust if the frequency of its power supply does not change. However, the speed of the HVDC or LVDC motor is adjustable. With the hydraulic efficiency of the pump 22 increasing, it is allowed to decrease the speed of the HVDC or LVDC motor 28, which helps to reduce the noise of the motor 28 and the washing apparatus 10. Further, the cogging torque of the HVDC or LVDC motor 28 is small and accordingly the motor 28 has a small circumferential vibration, which can reduce the vibration of the washing apparatus 10.

Although the invention is described with reference to one or more preferred embodiments, it should be appreciated by those skilled in the art that various modifications are possible. Therefore, the scope of the invention is to be determined by reference to the claims that follow.

In the description and claims of the present application, each of the verbs “comprise”, “include”, “contain” and “have”, and variations thereof, are used in an inclusive sense, to specify the presence of the stated item but not to exclude the presence of additional items. 

1. A washing apparatus, comprising: a washing chamber; a water supply path for supplying fresh water to the washing chamber; a drain path for discharging waste water in the washing chamber to the outside; and a drain pump for removing the waste water via the drain path, the drain pump comprising: a pump casing having a pump chamber, an inlet and an outlet which are in fluid communication with the pump chamber; an impeller received in the pump chamber; and a brush direct current motor comprising: a rotor comprising a shaft coupled to the impeller, a rotor core fixed on the shaft, a commutator fixed on the shaft adjacent the rotor core, and rotor windings wound on the rotor core and electrically connected to the commutator; and a stator comprising a magnetically conductive housing, at least one permanent magnet fixed to the housing, at least one pair of brushes making slide contact with the commutator, and at least two terminals for coupling an external direct current power supply to the brushes.
 2. The washing apparatus of claim 1, wherein further comprises: a detector being configured for detecting a load on the drain pump; and a speed regulator coupled to the detector and being configured for decreasing the speed of the motor to a speed greater than zero in response to the detector detecting an unload condition of the drain pump.
 3. The washing apparatus of claim 1, wherein the impeller comprises a base plate and a plurality of curved vanes disposed on the base plate.
 4. The washing apparatus of claim 3, wherein the pump casing is in a spiral shape.
 5. The washing apparatus of claim 4, wherein the drain pump further comprises a macerator disposed in the pump chamber and fixed to the shaft of the motor.
 6. The washing apparatus of claim 5, wherein the pump casing comprises a side wall and a top wall forming an annular step, the inlet extending outwardly from the top wall and the outlet extending outwardly from the side wall.
 7. The washing apparatus of claim 5, wherein the brush direct current motor is a high voltage brush direct current motor with a direct current power between 50˜400 volt being supplied.
 8. The washing apparatus of claim 5, wherein the brush direct current motor is a low voltage brush direct current motor with a direct current power between 4-36 volt being supplied.
 9. The washing apparatus of claim 8, wherein the flow rate of the drain pump is smaller than 60 litres per minute.
 10. The washing apparatus of claim 9, wherein an outer diameter of the magnetically conductive housing is between 35 mm-60 mm and an output power of the brush direct current motor is smaller than 60 watts.
 11. A drain pump, comprising: a spiral volute having a pump chamber, an inlet and an outlet which are in fluid communication with the pump chamber; an impeller received in the pump chamber and comprising a base plate and a plurality of curved vanes disposed on the base plate; a macerator disposed in the pump chamber and fixed to the shaft; and a brush direct current motor comprising: a rotor comprising a shaft coupled to the impeller, a rotor core fixed on the shaft, a commutator fixed on the shaft adjacent the rotor core, and rotor windings wound on the rotor core and electrically connected to the commutator; and a stator comprising a magnetically conductive housing, at least one permanent magnet fixed to the housing, at least one pair of brushes making slide contact with the commutator, and at least two terminals for coupling an external direct current power supply to the brushes.
 12. The drain pump of claim 11, wherein further comprises: a detector being configured for detecting a load on the drain pump; and a speed regulator coupled to the detector and being configured for decreasing the speed of the motor to a first speed greater than zero and smaller than a second speed when the detector detects the drain pump operates in a unload condition, the brush direct current motor operating in the second speed during a full load condition of the drain pump.
 13. The drain pump of claim 11, wherein the pump casing comprises a side wall and a top wall forming an annular step, the inlet extending outwardly from the top wall and the outlet extending outwardly from the side wall.
 14. The drain pump of claim 11, wherein the brush direct current motor is a high voltage brush direct current motor with a direct current power between 50˜400 volt being supplied.
 15. The drain pump of claim 11, wherein the brush direct current motor is a low voltage brush direct current motor with a direct current power between 4-36 volt being supplied.
 16. The drain pump of claim 15, wherein the flow rate of the drain pump is smaller than 60 liters per minute.
 17. The drain pump of claim 16, wherein an outer diameter of the magnetically conductive housing is between 35 mm-60 mm and an output power of the brush direct current motor is smaller than 60 watts.
 18. A pump, comprising: a pump casing having a pump chamber, an inlet and an outlet which are in fluid communication with the pump chamber; an impeller received in the pump chamber; an electric motor for driving the impeller; a detector being configured for detecting a load on the pump; and a speed regulator coupled to the detector and being configured for decreasing the speed of the motor to a first speed greater than zero and smaller than a second speed when the detector detects the pump operates in a unload condition, the brush direct current motor operating in the second speed during a full load condition of the pump. 